Brute's Spring Sting

In the coming month, each Louisiana resident will, at least once, shriek and flinch at a harmless dry oak flower. That’s because those fuzzy brown cylinders falling from the tree can look, at first glance, like that other fuzzy brown cylinder, the stinging buck moth caterpillar. Nearly everyone has a poison caterpillar story—and nearly everyone hopes to have only one.

The "why" of the sting is fairly straightforward: the more unpleasant it is for a bird to eat a certain caterpillar, the more likely it is to leave its nasty dinner’s cater-brethren alone, so that buck moths can continue to be fruitful and multiply. The "how" is more interesting. Zack Lemann, curator of animal collections at the Audubon Butterfly Garden and Insectarium, explained that buck moth caterpillars are covered with structures called urticating hairs, which they can’t control the way a bee or scorpion controls its sting. The hairs are attached to glands producing venom and will stick into anything that touches them, be it hungry bird, curious dog snout, or gardener’s hand. The best treatment for stings is a rinse with cold water and air dry; if you see stinging hairs still in the skin, draw them out with adhesive tape. Then, wait a week or ten days for the symptoms to fully subside. That’s about all you can do.

Buck moths are considerate in one way: unlike many butterfly and moth species that go through multiple generations in our encouraging climate, the buck moth only goes through one cycle a year, so there’s a defined and relatively brief “caterpillar season.” Adults emerge in autumn, provide food for migrating birds, and can be a pretty late-season sight with their gaudy orange rear ends. Alas, the buck moth caterpillar is only one of four main stinging caterpillar species to pester people and pets in South Louisiana; the saddleback and io moth caterpillars also have stinging hairs and will produce similar symptoms, and the silky-looking puss moth caterpillar packs an even more potent toxin that occasionally causes systemic effects. Some poisonous caterpillars present in other parts of the world can kill, so in a way, we’re lucky only to have these relatively mild stingers to contend with—next time, take solace when you’re enjoying a beer on the patio and one of them drops right onto you. Geronimo!